1. Field of the Invention
The present invention relates generally to aircraft performance management systems and more specifically to apparatus for computing the takeoff weight of the aircraft.
2. Description of the Prior Art
The takeoff weight of an aircraft is a critical parameter used by a pilot and/or a performance management system in determining climb, cruise, descent, holding and approach performance of the aircraft. Normally, the aircraft weight is the manifest weight determined by the operating company's procedures. The present invention provides a means for providing the pilot with a more accurate measure of the aircraft's actual takeoff weight by calculations involving the thrust imparted to the aircraft by the engines, the resulting acceleration and the average rolling friction characteristic of the landing gear during the takeoff procedure. Also, by calculating the average rolling friction factor, the pilot may be made aware of unusual takeoff conditions such as dragging brakes and the like for which maintenance action may be required. In performance management, the takeoff weight parameter computed by the present invention may be used to automatically compute climb, cruise, descent and approach parameters based on more accurate data than the manifest weight.
The present invention provides substantially improved performance with respect to the takeoff weight computer disclosed in the present inventor's U.S. Pat. No. 4,110,605 also assigned to the present assignee. In that patent, the rolling friction factor was assumed to be a known and constant value for a particular aircraft model. In practice, this is not the case for an individual aircraft and the present invention takes this into account to thereby provide a substantially more accurate measure of the aircraft's takeoff gross weight.